A method for generating a ground effect compensated aircraft body angle of attack signal is disclosed in the U.S. Pat. No. 5,089,968 of Orgun et al. As disclosed therein, the method includes converting an aircraft pitch rate correction alpha vane signal to a free air body angle of attack signal that is collaborated to the type of aircraft that employs the method for the two conventional landing flap settings. The free air body angle and attack signal is processed to obtain an alpha vane correction signal that represents ground effects compensation that would be required at zero altitude (touchdown). The zero altitude alpha vane correction signal is then multiplied by an altitude scaling signal and converted to a ground effect compensation signal that is applicable to the then current altitude of the aircraft. The ground effects compensation signal is summed with the free air corrected body angle of attack signal to provide the ground effect compensation angle of attack signal to provide the ground effect compensated body angle of attack signal of the patented device.
It is well known that the coefficient of lift increases with increases in angle of attack over a given range. However, if the angle of attack is increased beyond a given point, the lift coefficient is reduced. In such cases, the aircraft may become unstable or stall. It has also been recognized that aircraft during takeoff and climb out maneuvers are flown at relatively high angles of attack in order to maintain the proper lift force. However, in order to avoid unsafe conditions, a safety margin is provided for angle of attack and the aircraft is operated at less than its maximum performance characteristics.
It is now believed that there may be a large commercial market for a ground effects compensated angle of attack system that will allow a pilot to operate an aircraft at or near its maximum performance characteristics during takeoff i.e., during the first fifty or so feet of altitude. There should be a demand for such systems because they result in more efficient operation of the aircraft, ability to accommodate changing conditions and avoid obstacles. It is presently believed that the use of a ground effects compensated angle of attack method and system are particularly important during a takeoff maneuver when an aircraft is at its maximum loading.
Further, the ground effects compensated angle of attack system in accordance with the present invention can be manufactured and sold at a competitive cost, are reliable, durable and readily installed and serviced on an aircraft. Such system may also be readily added or retrofitted to many aircraft.